Reusable anode system for electrorefining processes

ABSTRACT

A reusable anode system for electrorefining processes allows eliminating the excess or scrap and generating a continuous electrorefining process having an increased contact surface between the anode and the electrolyte which comprises: a container ( 10 ) which is made of stainless steel and having the shape of a straight thin rectangular parallelepiped which on its front and rear faces has a plurality of holes ( 11 ) allowing the communication between the outside and inside in such a way the electrolyte is able to enter the container ( 10 ) wherein the upper portion of the container ( 10 ) is projecting higher than the position of the electrical contact bars ( 12, 13 ) by means of projections ( 16 ) extending the inside ( 15 ) of the container ( 10 ) to form an unloading and loading zone and (b) a plurality of copper bars ( 14 ) coming from an extrusion and wire drawing process is grouped inside ( 15 ) of the container.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a national phase application based upon priorityInternational PCT Patent Application No. PCT/IB2013/053635, filed May 6,2013, International Publication No. WO 2014/125341, published Aug. 21,2014 which is based upon priority Chile Patent Application No.C1447-2013 filed Feb. 14, 2013.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a reusable anode system forelectrorefining processes, constituted by a container which is made ofstainless steel and shaped as a straight thin rectangular parallelepipedhaving on its front and rear faces a plurality of holes communicatingthe outside and the inside in such a way the electrolyte is able toenter said container. In the upper portion, the container projectshigher than the position of the electrical contact bars, by means ofprojections extending the inside the container to form an unloading andloading zone for a plurality of copper bars. The copper bars coming froman extrusion and wire drawing process are grouped inside the container,thus forming the anode system of the present invention. This systemallows eliminating the excess or scrap of traditional processes of theprevious art.

BACKGROUND OF THE INVENTION

The production process of high-purity copper involves several stages,starting with the reception and sampling of copper concentrates. It isimportant to do a sampling thereof by classifying them according to theconcentration of copper, iron, sulfur, silica and impurities such asarsenic, antimony and zinc mainly.

Subsequent to the classification stage, the concentrate enters into thedrying stage wherein the humidity is reduced from 8% to 0.2%, then thedried concentrate enters into the fusion process, whose objective is toachieve a change of state which allows the concentrate to pass from asolid state to a liquid state so as the copper can be separated from theother elements comprising the concentrate.

The copper concentrate fusion is a product of the instantaneousauto-ignition thereof, which takes place at high temperatures (greaterto 1200° C.). In this process the concentrate passes from the solidstate to the liquid state, the elements comprising the ores present inthe concentrate are separated according to their weight, remaining thelighter ones on the upper part of what has been smelted (molten metal)which is called slag, mainly phases containing high contents iron andsilica, while the copper associated to sulfur which is heavier, isconcentrated on the lower part of the reactor, which is called Babbittmetal or bearing metal. Thus, it is possible to separate both parts bytaking them out from the reactor by means of tapping passages located atdifferent levels.

Fusion reactors and furnaces must be constantly loaded and permanentlytapped, the material having high content of copper is carried in liquidform through pots or channels to the conversion process where a highcopper phase called blister copper is produced (98.5 Cu). This productis subsequently carried in liquid form through pots or channels to arefining process where are mainly removed impurities such as dissolvedsulfur, dissolved oxygen and impurities such as arsenic, antimony,bismuth, lead among others, in such a way that finally it is possiblethe obtaining of the product called anode copper with an average purityof 99.5% of copper.

The anode copper is molded and solidified with a rectangular geometry,forming an anode plate (1) having ears (2) as showed in FIG. 1. The mostused form to cast the anode copper, is by means of a casting wheel,which comprises a determined quantity of copper molds, wherein copper ispoured at a temperature lower or equal to 1200° C., once the copper ispoured into the casting Wheel, the latter starts to spin and the smeltedcopper begins to cool off in a first stage at ambient temperature untilthe upper part of the copper is solid, subsequently the copper passes bya cooling stage which comprises upper water cooling and lower watercooling. In this stage the copper decreases its temperature untilreaching a complete solid state, to be carried to the electrolyticrefining plant in order to produce a high-purity cathode having coppercontents higher or equal to 99.9% Cu.

The anode copper is formed on a mold (7) which comprises a centralrectangular-shaped cavity (8) for receiving the liquid copper whichforms the anode plate (1). On the upper part of said mold (7) andtowards the corners of the central cavity (8) are located two cavities(9) for receiving the liquid copper which comprises the ears (2) as canbe seen in FIGS. 6 and 7.

In the refineries, the anode (1) is introduced in an electrolytic cell(3) which has a cathode (4) that can be permanent or of mother sheetaccording to the technology to be used, having its respective hangingbar (5). The electrolytic cell (3) is filled with an acid solution andcurrent is applied to the contacts (6) in order to produce theelectroplating of copper from the anode (1) towards the cathode (4)according to what is shown in FIGS. 2 to 5. In this process, the anode(1) only remains submerged up to the continuous zone of the ears (2) anddue to this, the upper part of the anode (1) does not participate in theelectrolysis process as shown in greater detail in FIG. 3, thus usingthe ears (2) only to transport the same and for electrical contact.

When finishing the electrolytic cycle, this part of the anode remainsintact and becomes an important part of the rest of the anode, togetherwith the undisolved material, called scrap. This material must be againsmelted to form a new anode (1) and continuing with the complete cycle.This product is formed in all the existing refineries and thereprocessing cost is high which is performed by means of differenttechnologies existing in the market.

The present invention proposes completely eliminating the excess ofscrap by means of the substitution of the molten and molded copper as ananode (1) with ears (2) by copper shaped as bars coming from anextrusion and wire drawing process which guarantees a surface qualityand homogeneity of the copper bar.

In order for these copper bars to be electro-refined, the presentinvention proposed the utilization of an anode system which comprises abars container having on its upper portion two projections for theelectrical contact in the form of ears and on its front and rear faceshaving a plurality of holes which allow the communication between theoutside and the inside of said container, in such a way the bars are incontact with the electrolyte.

There have been several attempts in the state of the art to minimize theresidues or scrap being produced by anodes coming from a casting processand which then pass to an electrorefining stage. Thus, for example,document CL 41874 published on Jul. 25, 2000, discloses a process torecover residues from copper anodes, by reusing them directly on thecasting mould to manufacture new anodes by means of casting. In thisdocument, it is indicated that currently the worn-out residues of coppermother anodes, extracted during the electrolytic processes are notreused in the same process and preferably are completely used as rawmaterial in the casting of copper to manufacture new “copper motheranodes” which subsequently return to the process, housing them in theelectrolytic cells as new pieces for the production of copper cathodes.This operation generates an additional cost when performing again theremelting, which makes the final product more expensive. A greatpercentage of these pieces (worn-out copper mother anodes) remain ingood condition right on the upper zone, wherein the electrical contactis produced in the electrolytic cells. This fraction of the piececonstitutes an important saving as regard to the material, therefore, ithas a great impact in the manufacturing cost of new “ copper anodes”.The saving is then generated by recovering and/or reusing the “worn-outcopper mother anode” after having completed its working cycle in theelectrolytic process, by using all or part thereof, as a wholeperforated and/or bent insertion or part thereof, in such a way it is aconstituent part of the “new copper mother anode” when placing it on themold and pouring liquid metal above the insertion by filling it up tocomplete a new piece, which after being cooled off can be demoulded tobe used.

On the other hand, there have been attempts to reduce the excess orscrap by means of the use of hanging bars with anodes being hung fromthese bars. Thus, for example, document EP 0284128 published on Sep. 28,1988 discloses a suspension bar for anode or a cathode sheet in theelectrolytic refining of metals wherein the core of the suspension barconsists of a material which exhibits a high resistance to bending and ahigh mechanical resistance, and being surrounded by a sheath of amaterial with good electrical conducting properties. This materialhaving good electrical conducting properties such as copper, near atleast one of the ends of the suspension bar and preferably near bothends, over a length of at least 3 cm and at most 5 cm, the sheath beingcontinuous to the end of the core. In addition, this document, disclosesa method for the manufacture of a suspension bar in which a sheath ofcopper is drawn over a core of steel, starting from copper tube. Copperand steel cores are introduced into the copper tube, subsequently thesheath is drawn with further cores being added, to a total length whichessentially corresponds to the change in length of the copper tubeoccurring as a result of the drawing and, finally, the rod produced issawn up into the desired rod lengths at the points where the coppercores are located. Towards the center, the bar has two hooks to suspendan anode or cathode as the case may be.

None of the previously mentioned documents discloses an anode systemcomprising: A bars container; and b) a group or set of copper barsallowing the elimination of the produced excess or scrap.

SUMMARY OF THE INVENTION

The present invention refers to an anode system comprising a barscontainer and a group or set of bars forming a reusable stainless copperanode manufactured in such a way that its structure is a container forcopper bars which are stacked inside thereof. The general shape of thisassembly is similar to the format of a smelted copper anode, both inmass and configuration, but when being formed by cylindrical solid bars,the total surface of the set of bars is by a 40% greater than itsequivalent in a flat smelted anode.

Since the copper in the electrorefining process must be dissolved in theelectrolytic solution by using a great amount of electric energy, theincreased surface has an impact in the speed of dissolution which isfaster due to the greater surface of copper in contact with theelectrolyte and for this reason when being faster, it is necessary touse a smaller amount of energy in order to achieve the same amount ofrefined copper deposited on the cathode.

Another advantage of this configuration is that as these bars aredissolved, they decrease their diameter, therefore they start compactingand being gathered in groups. As long as the system remains charged withcopper bars stacked on the upper part, which due to the weight starttightening and compacting the assembly, a constant dissolution of thebars will take place without the existence of copper excess or scrap. Inthis way, the electrorefining process can be maintained in a continuousway as the container is reload with copper bars.

Another advantage of the use of bars as anode copper mass lays in thatthe manufacturing process of bars involves an extrusion and wire drawingprocess which guarantees a surface quality and homogeneity of the copperbar. This surface quality is not feasible of being achieved by means ofthe current casting processes of smelted copper on open moulds.

Due to the aforementioned, an object of the present invention isproviding a system which allows completely eliminating the excess orscrap from the anodes processed in an electrorefining cell.

Another object of the present invention is providing a system whichallows a continuous electrorefining process by means of the reload ofthe containers of bars with new bars to be processed.

Another object of the present invention is generating a contact surfaceof the anode with the electrolyte which is increased by a 40% withrespect to the anode surfaces of the previous art.

A more detailed description of the invention is provided in thefollowing description and appended claims taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures are included to provide a better understandingof the invention. They are part of this description and serve to explainthe principles of this invention.

FIG. 1 shows a perspective view of an anode according to the previousart.

FIG. 2 shows a perspective view, according to the previous art, of anelectrolytic cell, having the anode and cathode inserted therein.

FIG. 3 shows a perspective view, according to the previous art, of anelectrolytic cell having the anode and cathode risen above the acidsolution (electrolyte).

FIGS. 4 and 5 show a perspective view of an electrolytic cell, accordingto the previous art, having the anodes and cathodes submerged in theacid solution (electrolyte).

FIG. 6 shows a front elevation of a casting mold to form an anodeaccording to the previous art.

FIG. 7 shows a perspective view of a casting mold to form an anodeaccording to the previous art.

FIG. 8 shows an exploded perspective view of the constitutive elementsof the system of the present invention formed by a container and copperbars.

FIG. 9 shows a perspective view of the system of the present inventionwherein the copper bars are inside the container.

FIG. 10 shows a schematic sectional view of the system of the presentinvention within an electrolytic cell wherein the bars are inside thecontainer.

FIG. 11 shows a schematic sectional view of the system of the presentinvention within an electrolytic cell wherein the bars are fed towardsthe container.

FIG. 12 shows a perspective view of a cell for the copperelectrorefining with the system of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The following is a detailed description and explanation of the preferredembodiments and best modes contemplated by the applicant and inventorsof carrying out the invention.

The present invention relates to a reusable anode system constituted bya container (10) which is made of stainless steel and shaped as astraight thin rectangular parallelepiped having on its front and rearfaces a plurality of holes (11) which allows communicating the outsideand the inside in such a way that the electrolyte is able to enter saidcontainer (10).

In the upper portion, the container (10) projects higher than theposition of the electric contact bars (12, 13) by means of projections(16) extending the inside (15) of the container (10) to form anunloading and loading zone of a plurality of copper bars (14).

The copper bars (14) coming from an extrusion and wire drawing processare grouped inside (15) the container (10), thus forming the anodesystem of the present invention. These bars (14) are shaped as cylindershaving a circular cross section.

With the surfaces (17) of the plurality of copper bars (14) it has awavy shape being formed by the plurality of semi-cylinders, said surfaceis greater by a 40% than the surface of the anodes of the previous art.

The anode system comprising a container (10) and the set of bars (14)located inside (15) of said container (10) is submerged in theelectrolyte within an electrolytic cell (3).

As the electrorefining process moves forward, the bars (14) startdecreasing their diameter and deposit at the bottom of the container(10) thereby causing that the bars (14) being on the upper part of thecontainer (10) are displaced towards the bottom portion of saidcontainer (10).

This allows the container (10) to leave an empty space on the upperspace where more bars (14) can be loaded in such a way of generating acontinuous process without removing the anode system of the presentinvention from the electrolytic cell (3).

The bars (14) whose diameter has decreased are deposited at the bottomof the container (10) until disappearing which leads to the eliminationof the excess or scrap.

Although embodiments and examples of the invention have been shown anddescribed, it is to be understood that various modifications,substitutions, and rearrangements of parts, components, and equipment,can be made by those skilled in the art without departing from the novelspirit and scope of the invention.

What is claimed is: 1-5. (canceled)
 6. A reusable anode system forcontinuous electrorefining processes comprising: (a) a container whichon its front and rear faces has a plurality of holes; and (b) aplurality of copper bars; characterized in that: said container is madeof stainless steel and having the shape of a straight rectangularparallelepiped, which upper portion projects higher than the position ofthe electrical contact bars by means of projections extending the insideof the container to form an unloading and loading zone, said upperportion of said container having an empty space wherein said pluralityof copper bars are loaded; and said plurality of copper bars coming froman extrusion and wire drawing process, which are grouped inside of saidcontainer, wherein said plurality of copper bars forms a surface of wavyshape, and wherein each bar of said plurality of copper bars has a shapeof cylinder having a circular cross section and that has a decreaseddiameter at the bottom of the container.